The present invention is directed to a method and apparatus for completion or recompletion of oil and/or gas wells with spoolable, flexible coiled tubing and retrieving the same.
In place of conventional drilling rigs or workover rigs, completions or recompletions of conventional oil and gas wells by coiled tubing have been disclosed in U.S. Pat. No. 4,844,166. However, the various completion equipment utilized, such as safety valves, gas lift mandrels and packers are rigid tools placed in the coiled tubing while the coiled tubing is being inserted into the well. In addition, the various completion equipment components are of a larger diameter than the coiled tubing (called upset). Since the completion equipment is rigid and has a larger outside diameter than the coiled tubing, these characteristics prevent the completion equipment from being run through a coiled tubing injector head. Therefore, equipment including windows must be provided to couple and splice this type of completion equipment in the coiled tubing string under the injector head. Furthermore, various specialized well control equipment, such as pack-offs and BOP stacks, were required because of the external upsets in the installation. Such installations were much more complicated to operate and required additional equipment when used with live wells which need to be pressure balanced.
The present invention is directed to a coiled tubing completion system which utilizes a continuous flush outside diameter length of coiled tubing and various completion components. The coiled tubing and the components are flexible and may be spooled onto a reel into lengths as long as 25,000 feet. The spool of coiled tubing and components is transported to the well site by a motorized vehicle and may be continuously injected into the well bore. As injection is occurring, a seal of well bore pressure may be more easily maintained around the circumference of the coiled tubing and components allowing the entire length to be placed in the well bore without a killing operation, eliminating the need for expensive kill fluids or damaging the formation. Included in the coiled tubing are various completion equipment, such as safety valves, annular control valves, concentric gas lift valves, packers, landing nipples, and sliding sleeves which are provided with an outside diameter flush with the coiled tubing out, side diameter and which are flexible, spoolable, and with through bores large enough to pass wireline tools for various well completion operations. In addition, some of this equipment, such as safety valves and annular control valves are hydraulically operated through a hydraulic control conduit which must not be upset to the outside diameter of the coiled tubing or interfere with the through bore of the coiled tubing. The coiled tubing completion system is simplified and cost is reduced since well control equipment that is normally required for handling external upsets in a production tubing is not required.